1. Field of the Invention
The present invention relates generally to an electroplating method, and in particular to an electroplating method by transmitting electric current from a ball side.
2. The Prior Arts
Due to environmental concerns, the electronics industry is moving rapidly to develop the lead-free and even the halogen-free materials. The lead-free soldereing processes require a higher reflow temperature than tin/lead applications. An increased level of heat resistance for the IC board is required to meet the requirements for the reliability of it when lead-free solder material is used. Therefore, the problems caused by the high temperature process should be solved by the product packaging manufacturer.
In order to improve the electrical properties and reduce the noise, the Bus less technology was applied to the IC board. However, the electroplated nickle/gold layer in the wire bonding region is still needed to achieve good adhesion. Although the nickle/gold layer can be formed by the electroless nickel immersion gold (ENIG) technology in the wire bonding region, the reliability of it is not good. Therefore, the electroplated the nickel/gold layer can be formed in the wire bonding region by the gold plating process (GPP) without the plating lines. However, the solder mask will cover the electroplated nickel/gold layer because the nickel/gold layer has been formed by electroplating process before the solder mask application. However, the material property of the solder mask greatly differs from that of the gold layer, and thereby the adhesion between the solder mask and the gold layer is potentially poor. Therefore, when the demand for reliability and heat resistance of the IC board becomes stringent, the conventional manufacturing method is not sufficient.
Moreover, for the non-plating line (NPL) process, the drawbacks of it is that the process is complicated; the specific equipment is needed to electroplate a thin copper layer; and the etch parameters are difficult to be controlled after electroplating the thin copper layer, which can cause micro short problem.
Therefore, the present invention provides a method in which the solder mask application is done before electroplating the nickel/gold layer without the plating lines in order to solve the problems set forth above.